Diffusion Behavior, Microstructural Evolution and Mechanical Properties of the 7A62 Aluminum Alloy During Homogenization

Abstract

The microstructural evolution and mechanical properties of semi-continuous cast 7A62 alloy during single and double-stage homogenizations were studied, and the diffusion behavior was analyzed. The results show that the secondary phases are effectively dissolved back during homogenization, and the alloy contains the minimum residual phases when homogenized at 465 °C. The hardness reaches the maximum value after 465 °C/24 h treatment and then decreases with the elevating of homogenization temperature. By comparison with the as-cast alloy, both the tensile strength and elongation of the 465 °C/24 h sample are significantly improved. Thus, the most appropriate single-stage homogenization for the 7A62 alloy is determined to be 465 °C/24 h. After the double-stage homogenization at 420 °C/4 h + 465 °C/28 h, the residual phases are fewer and the alloy elongation is further improved in comparison with the single-stage treatment. The diffusion kinetics of the alloying element atoms are investigated concerning the size and morphology of secondary phases. The strengthening mechanisms are also analyzed and related to the microstructure.